pkg/vcs: reset state even more

"git clean -fd" does not remove ignored files,
while can mess state when .gitignore changes across commits.
Use "git clean -fdx" to delete ignored files as well.

pkg/vcs/git.go

@@ -123,6 +123,7 @@ func (git *git) fetchRemote(repo string) error {
 
 func (git *git) SwitchCommit(commit string) (*Commit, error) {
 	git.git("reset", "--hard")
+	git.git("clean", "-fdx")
 	if _, err := git.git("checkout", commit); err != nil {
 		return nil, err
 	}
@@ -145,7 +146,7 @@ func (git *git) clone(repo, branch string) error {
 func (git *git) reset() {
 	// This function tries to reset git repo state to a known clean state.
 	git.git("reset", "--hard")
-	git.git("clean", "-fd")
+	git.git("clean", "-fdx")
 	git.git("bisect", "reset")
 	git.git("reset", "--hard")
 }